1. Field of the Invention
The present invention relates to an IC socket with which electrical connection between the contact terminal of a socket substrate and the electrode of an integrated circuit device (IC) is achieved by positioning the IC on the socket substrate and then closing a cover lid.
2. Description of the Related Art
FIG. 11 is a schematic cross section of the structure of a typical conventional IC socket. With this IC socket, a concave portion 3 that houses an IC 2 is formed in the center of a socket substrate 1. Contacts (contact terminals) 5 that are in contact with IC leads (electrodes) 4 for the IC 2 housed in this concave portion 3 are positioned in a row at a specific interval on the bottom of the concave portion 3. The contacts 5 are formed with a roughly U-shaped cross section such that they will have an upward resilience.
A cover lid 6 is rotatably attached to the socket substrate 1 via a hinge 7, and the cover lid 6 is energized in the direction of the arrow a by a coil spring (not shown). To the other end of the cover lid 6 is attached a stop lever 9 that has a hook-shaped leading edge 8, and the stop lever 9 is energized in the direction of the arrow B by a coil spring (not shown). A pressing component 10 that presses against the IC lead 4 from above is rotatably supported on the back side of the cover lid 6 with a shaft 11 as its fulcrum.
A step 12 is formed on the other end of the socket substrate 1 at a location corresponding to the leading edge 8 of the stop lever 9. When the IC 2 is housed in the concave portion 3 of the socket substrate 1, the contacts 5 of the socket substrate 1 and the IC lead 4 of the IC 2 are brought together, and the cover lid 6 is closed, then the leading edge 8 of the stop lever 9 engages with the step 12 of the concave portion 3 so that the socket substrate 1 is fixed to the cover lid 6. At this point, the IC lead 4 resists the resilience of the contacts 5 and presses against the contacts 5 through this pressing force by means of cover ends 10a formed on the lower end of the pressing member 10, thus ensuring good conduction between the IC lead 4 and the contacts 5.
With the conventional IC socket described above, a row of IC leads 4 can be pressed substantially simultaneously with a substantially perpendicular pressing force by means of the pressing member 10, so there is no distortion of the IC leads 4 caused by unbalanced load when the cover lid 6 is closed. However, with an IC socket structured as above, since the movement of the pressing member 10 is limited solely to rotation around the shaft 11, the pressing member 10 undergoes a positional shift in the lateral direction when the cover lid 6 is closed centering around the hinge 7. This is explained graphically in FIG. 12.
FIG. 12 is a diagram of the locus of the shaft 11 when the cover lid 6 is closed. In FIG. 11, if we assume that the shaft 11 is in the position a shown in FIG. 12 when the covering end 10a of the pressing member 10 comes into contact with the IC leads 4, then the shaft 11 moves from position a to position a', which means that the position of the shaft 11 has shifted by At when viewed from above.
Specifically, since lateral shifting occurs with a conventional IC socket when the pressing member 10 presses against the IC leads 4, there is a positional shift between the IC leads 4 and the corresponding contacts 5, and this is a problem in that poor conduction between the leads of the IC and the contacts of the socket results, making impossible the normal operation of the IC.
Even with a leadless IC where signal pads as electrodes are provided, lateral shifting of the IC itself occurs just as with the lead-attached IC discussed above, so there is a positional shift between the contacts and the signal pads installed on the back, and this can lead to poor conduction therebetween.